President Obama hobnobbed Wednesday night with big-money Democratic donors during a whirlwind visit to the Hub that added to traffic snarls during evening rush hour and drew protesters on issues foreign and domestic.

Obama first joined roughly two dozen supporters who gave up to $32,400 at a Democratic National Committee roundtable discussion at the Charles Hotel in Cambridge, according to a committee official. The event was closed to reporters.

He then proceeded to a DNC dinner at the Artists for Humanity EpiCenter in South Boston, where about 75 supporters had paid $5,000 to $20,000 per ticket, the official said.

As the president zipped across the city, portions of the Massachusetts Turnpike were briefly closed to traffic, while MBTA commuter rail and bus service were halted for about 10 minutes, authorities said.

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As Obama left the Charles Hotel, his motorcade passed more than 100 protesters standing behind barricades in frigid temperatures, many voicing support for the fledgling government of Ukraine, now in a tense faceoff with Russia.

Some protesters chanted and several held aloft yellow-and-blue Ukrainian flags and signs with messages including “Putin Nyet” — a “no” to President Vladimir Putin of Russia, whose troops seized control of much of Ukraine’s Crimean peninsula on Saturday.

More demonstrators rallied outside the EpiCenter, home to an organization that helps young people develop creative abilities and find jobs in the arts.

The activists oppose the proposed Keystone XL pipeline, a 1,700-mile conduit that would carry oil from Canada to the Gulf of Mexico.

Adam Greenberg, who took part as a member of a grass-roots organization addressing climate change, said the group gathered to ask the president to safeguard the environment, as protesters have done for months at events Obama has attended.

Inside, Patrick introduced the president with remarks critical of the GOP. “What we have right now is a Republican Party that brings us gridlock and shutdowns, and fiscal cliffs, and debt-ceiling crises, and a whole host of other totally avoidable crises,” Patrick said.

Obama’s 13-minute speech addressed progress he said the United States has made on the economy, health care, and rights for lesbian, gay, bisexual, and transgender citizens.

“We have all the ingredients to make sure the 21st century is an American century, just like the 20th,” he said.

Obama spoke of the nation’s minimum wage, which he supports increasing, saying “the majority of the country, including half of Republicans, agree with” me.

He called on Democrats to avoid being complacent in this year’s congressional elections.

“In the midterms, Democrats, too often, don’t vote,” he said. “And because the electorate has changed, we get walloped. It’s happened before, and it could happen again if we do not fight on behalf of the things we care about in this election.”

Obama said that though he is not on the ballot, the ideas that he cares about are.

“The progress we’ve made is on the ballot. The things that Deval has fought for here in Massachusetts are on the ballot,” he said.

“This counts. And I’m going to need you guys to step up,” the president said.